Electric valve translating apparatus



June 24, 1941. J. w. BoAG ET AL ELECTRIC VALVE TRANSLATING APPARATUS 4Sheets-Sheet l Filed Feb. 5, 1940 i W .mam m P O e O oBRt m WWWWM mmmIJJ T June 24, 1941- J. w. BoAG ETAL 2,247'073 ELECTRIC VALVETRANSLATING APPARATUS Filed Feb. 5, 1940 4 Sheets-Sheet 2 u'n n'n' 50Inventors: John VV. Bog, John C. Read,

by Th ir` Attorney.

ELECTRIC VALVE TRANSLATING APPARATUS Fila Feb. 5, 1940 4 Sheets-Sheet 3T0 MAIN ANODES M T0 AUXILIRYANODES Fg. IZ.

T0 AUX I LIARYANODE 5 TO MAIN ANODES Inventors: John VV. Boag, John C.Read,

June 24, 1941. 1.w. BOAG TAL ELECTRIC VALVE TRANSLATING APFARATUS FiledFeb. 5, 1940 4 Sheets-Sheet 4 FILTER CIRCUITf-f Inventors: John VV. BoagJohn C. Read by Patented June 24, 1941 ELECTRIC VALVE TRAN SLATIN GAPPARATUS John W. Boag and John C. Read, Rugby, England,

assignors to General Electric Company, a corporation of New YorkApplication February 5, 1940, Serial No. 317,450 In Great BritainFebruary 9, 1939 11 Claims.

Our invention relates to electric valve translating apparatus and moreparticularly to electric valve circuits for transmitting power betweenalternating current circuits and direct current circuits.

In electric vvalve translating circuits for the transmission `of powerbetween alternating current circuits and direct current circuits, it isdesirable to employ a relatively large number of electric dischargepaths in order to improve the wave form of the currents supplied to theload circuit. For example, in the transmission of power from alternatingcurrent circuits to direct current circuits, it is important in manyapplications to employ multi-phase rectifying systems in order that thewave form of the direct current voltage is relatively smooth and devoidof abrupt changes in magnitude which would be present by using a smallernumber of phases. In addition, it is desirable to use arrangements whichpermit the simultaneous operation of two or more of the electricdischarge paths so that the utilization or utility factor of therectifier phases is maintained at a relatively large value. Rectifiercircuits have accordingly been developed which operate so that two ormore anodes carry current simultaneously and during a considerablygreater portion of the voltage cycle than ythat which occurs in the caseof simple multi-phase rectifier circuits. Many of these systems functionby using what is termed phase equalizing or interphase transformingmeans. In arrangements of this nature, successive phases or independentphase groups are electromagnetically coupled so as to produce anodevoltages which are more or less trapezoidal in wave form compared to thecombined sinusoidal voltages of the simultaneously operating phases.Rectifier circuits employing interphase transformers ,or phaseequalizing means may, therefore, be characterized by the features thatas many anodes carry current simultaneously as there are couplingsbetween phases or phase groups, and that the output voltage at anyinstant is equal to the mean of the voltages of the simultaneouslyOperating phases.

In accordance with the teachings of our in- Vention describedhereinafter, we provide new and improved phase equalizing or interphasetransforming means whereby the Wave form of the delivered voltage issubstantially improved. Our invention relates to improvements ininterphase transforming circuits such as that disclosed and claimed inco-pending patent application Serial No. 262,542 of Heinz Puppe. Forexample, our system relates to interphase transforming means whereby arectifying system, adapted to operate as a six-phase rectifier, can becaused to yield the approximate equivalent of twelve-phase operation byconnecting small additional anodes or rectifying devices to suitableadditional or auxiliary windings provided on the interphase transformer.We have found that certain predetermined ratios of the number of turnsof the main windings to the number of turns of the auxiliary windings ofthe interphase transformer afford highly desirable results in Wave form.

It is an object of our invention to provide new and improved electricvalve translating circuits.

It is another object of our invention to provide new and improvedinterphase transforming means for polyphase electric valve rectifiersystems.

It is a further object of our invention to provide new and improvedinterphase transforming means in which the turn ratios are fixed toobtain desirab-le output voltage characteristics.

Briefly stated, the present invention may be described as relating to anelectric valve rectifier equipment having np main phases where np isgreater than six, and which are divided into n similar groups of pphases per group, and the neutral points of the n groups being connectedto the main neutral point by means of an n phase interphase transformer.The interphase transformer has auxiliary windings provded on its nphases, with a suitable turn ratio more particularly definedhereinafter, and these auxiliary windings are connected to n auxiliary'rectifying devices to obtain the approximate equivalent of 211p phaseoutput voltage.

For a better understanding of our invention, reference may be had to thefollowing description taken in connection with the accompanyingdrawings, and its scope will be pointed out in the appended claims. Fig.1 diagrammatically illustrates generally an application of an auxiliaryrectifying means and an interphase transformer having auxiliary windingsfor controlling the output characteristic of an electric valverectifier, such as that broadly disclosed and claimed in theabove-identified copending patent application of Heinz Puppe. Fig. 2represents certain Operating characteristics of the arrangement shown inFig. 1. Figs. 3-11 represent certain modifications of our invention asapplied to n-phase rectifying systems in which the interphasetransforming means assumes various forms and in which the turn ratioshave denite values to obtain the desired output voltage characteristicsof the electricvalve rectifying system. Fig. 12 illustrates a'modification of the embodiment of my invention shown in Fig. 11 asapplied to groups of polyphase transformers in-- terconnected throughinterphase transforming,

means.

Referring now to Fig. 1, the broad principle V underlying our inventionma-y be expl'ained by referring to the electric valve'translating system|shown in Fig. 1. A polyphase electric valve rectifier l having aplurality of anooles-'-;and'av cathode 3 is connected to two inductivenetworks: 4Land' 5;

for itransmitting power to the direct current .circuit, includingconductors 6 and 1, from* the polyphase alternating. currentcircuit. 8throughV a transformer 9; having; primary Windings I and secondarywindings H; and |-z2v which constitute the: inductive: networks 4. and5... The secondary windings.: M and' I'2' may 'be arran'ged to.y formadouble-star connection having; the respectivesystems.: of: phasewindings displaced-sixty electrical degrees.. 'I'ie electricvalvemeanslmay also bev providedf Wit-h control members. or `grids. E3: to controlthe magnitude of. the outputvoltage impressedon the direct' current loadcircuit. An

interphase transformer having a main winding Hand auxiliary winding and:IG: is connected between. the inductive networks liand En to increasethe uti1ization factorof the electric. valve translating 'system and tolimprove the wave form oftheoutput voltage. The intenphase transformerproduces an equalizing voltage which tendsy to maintain. an equal.current distribution between'v thev simultaneously Operatingl phases.This. equal voltage is a harmonic.. voltage determined by-thenumber of`phases of. the groups 4 and 5; that is, inthe form shown in. Fig.. 1the.

harmonia voltage is a ;third harmonia. An auxiliary rectifying means ITincluding, aplurality of electric discharge. paths connected to. theauxiliary windings. I'5. and l`rof theV int'erphase transformer andserves. t'o. conduct currentzito the load circuit inparallel with. the.are: discharge paths of the main-electric: Valve means I; IJ'he electricvalve means |-`l may include. a plurality of. anodesz IB: and.associated; grids |9'. Asuitable ci'rcuit controlling, means. such as.a. circuit breaker gmay be connected'between the electric.

valve. means; l' 'and' the positive terminal; of'. the direct. currentcircuit. to.` connect. the: auxiliary rectifier If'l' and theauxiliarywindings; of the in- 4, and curves D, E and F represent thephase Voltages of the secondary windings |2 in network 5. The resultantcurve G represents the output Voltage of the rectifier employing theinterphase transformer without use of .the auxiliary windings [5 and |6.That is, curve G rep'resents the mean phase voltage of both networks 4and 5. Each of the secondary windings ll and 12 conducts current forelectrical degrees but fo-r only 60 electrical degrees with any oneother phase winding in another group. The -curve H representsthe thirdharmonicvoltfage; which appearsacross the' terminals of thewindings ofthe interphase transformer and which effects equal- -ization of theinstantaneous phase Voltages to causet-hewindings which are displaced inphase tor conduct current simultaneously. Curve J represents the outputvoltage obtainable When thecircuit breaker 20 is closed, efiectivelyconnecting. the=rectifierv l'l in the system. It will be noted th'at'theripple of `the output volage represented'by curvev J corresponds to thatof a twelvephase system..

Referring now to Fig'. 3, oul` invention is there illustrated' asapplied to an electric valve means 2.!-` having' a. pluralityof:ano'desl: associated grids; 23%. The electrdvalve means: 21a may' havetwelve anodesenergized: from:` foursindiictive net.- Works 24:-2"l=,inclusiv. connected. to form. two: sixt-phase double-star connections.It will. 'beunderstoodithat inductiye; networks andfi 2Ei=in conjunctiomwith interphaseitransformer lZform. asix-phase doubleestar connectionyand'that net"- works and 21' andthe' intenphase transformer.

29. also form asix-phase double-star: connection.

A. third int'erphase transformer 30; mayf beconnected' between theVinterphase: tizansformers'` 28%. and 29. and the negativeterminal:offthe direct current. circuitz. The.4 phase windings. or:1 the phasevoltages of theV imo-asystemszare. displaced-V fifteen electricaldegrees'. by: virtuaofi the':zigzag connections.. Interphasetransformer' 2,8'- is' pro-- vided: with: a' pair of oppositelyfdisposed mainJ winding sections:A 3.15 and: ;itanda pair of auxiliary'windings 3'3 and Fonzthepurpose of representing the. turruratios of: thevarious Sections of-` the windings. of:theinterphaseetransformers thelportions; of' themain vwiindi-ngs'` will k:e-re;o1'esented-E by y and;the number: of.v turns.v off the auxillaryJ Windings will: be;representedf Joy`y 'I-'he neutral! connections 35 and= 3.6: of thenetworks 271i and Z5`- are connected -toa the junctures-of? theauxili'ary winding Sections anct the main: windingl Sections oftheinterphasetransformers. i w

We provide an auxiliaryf reciiifying" means; 3-1I` comprisinga..pluralityy ofi auxiliany electric discharge paths; includingapluraliiy of anodes' 38: and. a .cathode 391.. The electric'dischargepathsV may be.- of; the: controlledz' type having' associated'grids: z The.. anndes 38: correspoi'iol1 i'n number to: the. totalnumber' of: amiiliaryf winnii'igsV of i'nhl on the. direoucurrent. loadcircuitfcomprising con- We have. found.. that' the turn duct'ors. 6 and`TF. ratio:

in the inter-phase transformers 2-81 and- 28. for.-

satisfactory operationis. approximately. 5.46;

The rectifier system of. 3 operateszso'that the inductive networks` 24and. 25,| form: a. six-. V

phase; system, and. the. aux-iliary'a'nodes: connected.

to auxiliary windings 33 and 34 of the interphase transformer 28 inconjunction with the associated anodes 38 convert this system to anapproximate equivalent of a twelve-phase system. Similarly, inductivenetworks 26 and 21 and the associated interphase transformer 29 andauxiliary anodes I38 in turn operate as another equivalent twelvephasesystem. Since these two twelve-phase systems are displaced by fifteenelectrical degrees relative to each other, the complete system is theapproximate equivalent of a twenty-four-phase system. This connectionis, however, for some purposes less `advantageous than those which willbe hereinafter described inasmuch as with the auxiliary anodes 38disconnected, it reverts not to twelve-phase operation but to a modifiedform of six-phase operation.

This feature of the arrangement shown in Fig. 3 is obviated in theconnections shown in Figs. 4 and 5. In Fig. 4, two six-phase double-starconnections are employed, each displaced by thirty electrical degrees.In the arrangement of Fg. 4, the inductive networks 4| and 42 areinterconnected through an interphase transformer 43, and the inductivenetworks 44 and 45 are interconnected through an interphase transformer46. The two six-phase double-star systems are interconnected through theinterphase transformer 41 having a main winding 48 comprising twooppositely disposed sections, and having auxiliary windings 49 and 50.The auxiliary windings 49 and 55 are, of course, connected to a pair ofauxiliary electric discharge paths as shown in Fig. 1.

The phase displacement between the two sixphase systems in thearrangements of Figs. 3 and 4 may be obtained either by zigzagconnection of the secondary windings or by providing the two six-phasesystems with separate primary windings and suitably connecting the phaseconnections of the primary windings in accordance with transformerconnections well known to those skilled 'in the art.

Similarly, in Fig. 5 two six-phase triple-star systems 5| and 52 areconnected to operate together, the respective phase voltages thereofbeing displaced thirty electrical degrees from each other and areconnected to the interphase transformer 41. In both Figs. 4 and 5, theinterphase transformer 41 is arranged to have a turn ratio ofapproximately 27.321; that is, the ratio of the number of turns of theauxiliary windings 49 and 50 to the associated sections of the mainwinding 48 is 27.3. Either of these systems affords the approximateequivalent :of twlentyfour-phase operation and reverts to twelvephaseoperation if the auxiliary anodes |8 are disconnected from the system.

The transformer connections described above are, generally speaking,specialized cases of a general system. In the general case a rectifierhaving np main phases may be considered as having n similar groups of pphases per group, the phase displacement between phases in a group being21r/p. The neutral points of the n groups are connected to an n phaseinterphase transformer; and the auxiliary windings on the 7b phases ofthis interphase transformer are connected to n auxiliary rectifyingdevices.

In Fig. 6 this general case is illustrated for the arrangement where nis equal to 4 and p is equal to 3; that is, the secondary windings ofthe main transformer supplying the main anodes consists of fourthree-phase star-connected systems 53, 54,

55 and 56, displaced apart by thirty electrical degrees. The neutralconnections 51 of the starconnected windings 53-55 are connected towindings of interphase transforming means in- .cluding legs 58, 59, 60,and 6|, respectively. The interphase transforming means may beconsidered as a four-phase interphase transformer to provide the commonnegative terminal of the direct current circuit comprising conductors 6and l. This interphase transforming means may be constructed to have afour-leg magnetic core structure such as that disclosed and claimed inUnited States Letters Patent No. 1,794,246, granted February 24, 1931,on an application of John C. Read. Associated with each leg of theinterphase transformer we provide a main Winding 52 and an auxiliarywinding 63, the common juncture 64 of which is connected to the neutralconnection 51 of the associated star-connected inductive network. Theauxiliary windings 63 are connected to the auxiliary rectifier 31 whichoperates in parallel with the main rectifier 2 I The turn ratio of theinterphase transforming means is made approximately equal to:

This turn ratio produces effects on the alternating current supplycircuit and the direct current load circuit closely equivalent to arectifier equipment having 27m phases.

In accordance with another feature of our invention shown in Figs. 7aand 7b, we provide improved interphase transforming means forinterconnecting the main transformer windings, the interphasetransforrner and the auxiliary rectifying devices. For example, in thearrangement of Fig. 7a, the magnetic circuit of the n phases, Where n isequal to 4, may have n legs and each leg carries two main windings 65and 66 connected in oppositon and which are connected in series relationto the neutral points of the associated star inductive network, such asthat shown in Fig. 6. The respective phase groups of the individualnetwork are displaced in phase by 21r/7Lp electrical degrees. Each legof the interphase transforming means also includes two auxiliarywindings 61 and 58 similarly connected. The auxiliary windings, ofcourse, are connected to the auxiliary electric discharge paths. Theturn ratio is established by the same expression as stated above inconnection With the arrangement of Fig. 6 and the Operating results arequite similar, that is, are approximately equivalent to a rectifierhaving np phases.

Fig. 7b is substantially the same as that explained above in connectionwith Fig. 7a and corresponding elements have been assigned likereference numerals. In the arrangement of Fig. 7b, however, theauxiliary windings 68 are connected in circuit with a main winding of adifferent phase of the interphase transforming means.

Fig. 8 diagrammatically illustrates an arrangement of an electric valverectifying system in which the main anodes are supplied by a transformer69 comprising primary windings 10 and 'H and groups of secondarywindings 12-15.

The groups of secondary winding-s 12-15 are arranged'V in what iscommonly known as a twelvephase quadruple zigzag with double primarywindings. The four neutral points 16 of the secondary windings areconnected 'to interphase transformer 'Il which may be of the type shownin Figs. 7a and 7b having a core structure comprising four magnetic legseach leg having associated main windings 65 and 66 and auxiliarywindings 61 and 68. The turnv ratioV is determinedi in accordance withthe expression given above and isapproximately x:y=2.76:1 Thisarrangement in operation is approximately the equivalent oftWenty-four-phase system, The amount of power which the auxiliaryrectifier .31 is required to transmit is a very small proportionl of thetotal power transmitted by the system. If desired, a suitable filtercircuit may be connected across the terminals of the direct currentcircuit to absorb undesirable voltage characteristics'.

An advantage of these arrangements, such as that shown in Fig, 8, is thefact that it is possible to install a rectifier initially to operate inthe usual way Well known and to convert this at a later time to yieldapproximatelythe equivalent of a rectifier system having a double numberof phases if subsequent conditions prove such operation to be desirable.That is, a system may be initially installed to have np phases and byadding the auxiliary rectifier equipment to. the interphase transformerthe system may he made to operate with a 271p phase characteristic. Sucha conversion could be effected either by initially constructing theinterphase tr'ansformers with the necessary auxiliary windings or byreplacingA the. auxiliary transformers by interphase transformers. withthe necessary auxiliary windings. As a further arrangement, the systemcould beinitially built in accordance With the circuit diagram shown inFigs, 9 and 10 in which the original interphase transformers are left inuse and an additional interphase transformer may be connected inparallel relation with them in the manner shown to supply the auxiliaryrectifier.V ThusinFig. 9 theloriginal six-phase double-star transformerincluding windings 18 and 19. and aninterph-ase transformer 80 may beconverted to an equivalent twelve-phase system by employing anadditional interphase transformer 8| havingA main winding sections andauxiliary winding sections. The turn ratio m-ay be established to havethe following value: m:y=5.46:1 It is not necessary that the originalinterphase transformers be of the same connection as the auxiliaryinterphase transformers thus connected in parallel with them providedthat the voltagesV acrossthe transformer to neutral are of the same formand effect division of the np phase rectifier intothesame number of ngroups. Thus, in Fig. 10 a twelve-phase rectifier comprising groups ofstar-connected. windings .82-85. and interphase transformers 8.6, 81 and88 may be provided' with an` auxiliary interphase transformer 89 of thetype described above in connection with Figs. 7a, 7b and 8; Theauxiliary interphase transformer 89 Supplies the auxili'ary anodes 38of' the auxiliary rectifier 31 to convert the equipment to anapproximate equivalent of a twenty-four-phase system. As in Fig. 8, theturn ratio of :czy is approximatelyV 2.76. r i

Avparticular advantage of the arrangement shown inFig. 19 and also ofthe arrangement shown. in Fig. 12, described hereinafter, is that. theinterphase transformer 89, on which the auXi-l-iary windings 61 and- 68are wound', does not carry the direct current components of the mainanode currents so that its core is not susceptible toA direct currentsaturation in the event the currents 'become 'unb'alanced The mostlikely form of such unbalance is that due- -tothecurrents fiowing in thetwo halves or secondary windings of the interphase transformer 88. Inpractice, this latter interphase transformer can be readily designed orarranged to carry such unbalanced currents without its action beingimpaired', 'Ihe arrangement shown in Fig. 9 also has this ad- Vantage,but it is of less value in that instance since unbalance of the currentsin the two halves of the main anode system is much less likely to occurin a six-phase system than in a twelvephase system.

Any main transformer connections aifording balanced np phase operationcan be used in conjunction with any of the 'n phase interphasetransformer arrangements described above. For example, the twelve-phasemain transformer connection illustrated in Figs. 6, 10 and 12 areinterchangeable with the quadruple zigzag twelvephase connection withdouble primary windings illustrated inl Fig. 8. Furthermore, the lattermay have a single three-phase primary winding with the reactancesbetween windings so adju-sted as to give balanced operation in atwelve-phase system.

Fig. 11 shows an application of our invention to a twelve-phaseconnection in which n i's equalV to' three and p is equal to four andhaving a turn ratio of x:y=7.24:1. As in the other connections, the 30degree electrical phase displacement between main transform'er phasescould equally well' be obtained by zigzag connections. In thearrangement of Fig. 1'1, the main anodes of theelectric Valve means (notshown) are energizedfrom a plurali-ty of single phase windings -95 eachhaving a neutral 'connection 9B, and are energized from the alternatingcurrent supply circuit 8 through primary windings 91 and 98 of theassociated tran-sformer. A closed delta tertiary winding 99 may also beemployed in the mannerV well understood by those skilled in the art. Thetertiary winding 93 is so constructed that its impedance to the flow oftriple harmonia I cu'rrents is made relatively small to perinit the fiowof third ha-rmonicv currents. The inter-- phase transfermer 300 ispreferably of the type comprising a core structure having three legseach of which is provided with two auxliary windings' mi and' l'-Z, andtwo main windings N33 and HM.

Of course, in all instances the'auxiliary anodes may be protected byfuses or reactors'. In the instance where the interphase transformerincluding the aux-iliary windings does not carry the load currentof'the'main anodes, suchas in Figs. 9, 10', and 12, the protectiveequipment, which maybe a fuse or a switch 185, may be connected' betweenthe nia-in transformer system and the' auxiliary transformer system.

It is to be understood that it is undesirable to destroy the symmetry"of operation of the main rectiferV i'n the event of any dissymmetry ofoperation of the-au'xil'iary rectifier''l. The switch may be made tooperate'in response'to any such di'ssymmetry to disconnect the auxiliaryinterphase transformer upon theV occurrence of erratic or irregularVoperation.

In' Fig. 1'2 a further modificati-on of our invention is shown. It isimmaterial' in the practice of our` invention as to whether or not theinterphase transformer is connected to the phase term'inals of the mainwindings, as discussed above, or whether the interphase transformers areconnected directly to the main neutral points. It is to be understoodthat wherever one or the oth'er type of interphase transformer is shown,the other type may be used; that is, Fig. 12 shows how the connection ofFig. may be modified if the interphase transformer is connected as anauto-transformer. In the arrangement of Fig. 12, the turn ratio is, ofcourse, :y=2.'76:l.

In all of these connections where interphase transformers between theneutral points of the n phase groups have been referred to, it wouldalso be possible to use alternatively other connections which are theequivalent of such interphase transformers. That is, the ordinaryconstruction of an interphase transformer having n phases of its mainwindings which are connected to n neutral points may be employed.Therefore, each phase of the interphase transformer carries the combinedcunrent of the p phases which constitute a phase group. But, it would beequally sati'sfactory if, instead of combining the currents of the pphases in this manner in a single winding, the ampere turnscorresponding to the currents could be combined in the interphasetransformer in any other way such a's by providing in the interphasetransformer p closely interlinked coils in series with the respective panodes, instead of one coil carrying the combined current of the panodes.

While we have shown and described our invention as applied to particularsystems of connections and as embodying various devices diagrammaticallyshown, it will be o-bvious to those skilled in the art that changes andmodification's may be made without departing from ,our invention, andwe, therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit andscope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States, is:

1. In combination, an alternating current circuit, a direct currentcircuit, electric translating apparatus connected between said circuitsand comprising a plurality of electric discharge paths and n groups ofelectrically displaced phase windings, each group comprising p phasesand each having an electrical neutral connection, an interphasetransformer connected between the neutral connections of said groups andhaving auxiliary windings, the turn ratio of said interphase transformerbeing:

where :c represents the number of turns of the auxiliary windings and 'yrepresents the number of turns of the main portion of the interphasetransformer winding, and auxiliary rectifying devices connected to saidauxiliary windings and connected to operate in parallel with said firstmentioned electric discharge paths.

2. In combination, an alternating current circuit, a direct currentcircuit, electric translating apparatus connected between said circuitsand comprising a plurality of electric discharge paths and comprisingtwo six-phase double-star inductive networks connected in parallel, apair of interphase transformers each associated with a different one ofsaid group and each having a pair of opposing main windings and opposingauxiliary windings, the turn ratio of the main windings to the auxiliarywindings being:

where a: represents the number of turns of the auxiliary windings and yrepresents the number of turns of the main windings, and two pairs ofauxiliary rectifying devices connected to the auxiliary windings of thetwo interphase transformers and connected to operate in parallel withsaid first mentioned electric discharge paths.

3. In combination, an alternating current circuit, a direct currentcircuit, electric translating apparatus connected between said circuitsand comprising a plurality of electric discharge paths and comprisingtwo six-phase doublestar inductive networks displaced with respect toeach other by sixty electrical degrees, an interphase transformerconnected between said networks to cause said networks to operate inparallel to form a twelve-phase system, said interphase transformerhaving a pair of oppositely disposed main windings and a pair ofoppositely disposed auxiliary windings, the ratio of the turns of theauxiliary windings to the main windings being approximately 27.3, and apair of auxiliary electric discharge paths each connected to a differentone of said auxiliary windings to cause said system to operate in effectas a twenty-four phase system.

4. In combination, an alternating current circuit, a direct currentcircuit, electric translating apparatus connected between said circuitsand comprising a plurality of electric discharge paths and comprisingtwo six-phase triple-star inductive networks displaced thirty electricaldegrees, an interphase transformer for causing said networks to operatein parallel and comprising two oppositely disposed main windings and twoopposite disposed auxiliary windings, the ratio of the turns of theauxiliary windings to the main windings being approximately 27.3, and apair of auxiliary electric discharge paths each connected to a differentone of said auxiliary windings for causing said networks to operate ineffect as a twenty-four phase system.

5. In combination, an alternating current circuit, a direct currentcircuit having positive and negative terminals, electric translatinlgapparatus connected between said circuits and comprising a plurality ofelectrical discharge paths and four three-phase star inductive networksdisplaced from each other by substantially thirty electrical degrees andeach having a neutral connection, interphase transforming meansincluding four windings each having a terminal connected to the neutralconnection of one of said networks and each having a terminal connectedto the negative terminal of said direct current circuit, and fourauxiliary electric discharge paths each connected between a differentone of said windings of said interphase transforming means and thepositive terminal of said direct current circuit.

6. In combination, an alternating current circuit, a direct currentcircuit having positive and negative terminals, electric translatingapparatus connected between said circuits and comprising a plurality ofelectric discharge paths and four three-phase star-connected inductivenetworks displaced thirty electrical degrees, an interphase transformercomprising four legs each comprising two main winding Sections and reachcomprising two auxiliary 'winding Sections, :each of the main windingSections :being connected in v:Seriesrelation `with another main'winding section on a different leg and each of the auxiliary windingSections being connected in series relation with an auxiliary windingSecftionon fa Vdifferent leg, and four auxiliary elec- 'tricfdischargepathS connected to the auxiliary .winding Sections.

In combination, :an alternating current'circuit, fa direct 'current=circuit ``having positive -and negati-ve iterminals, electrictranslating apparatus :connected 'between Said circuits and comfpriising.a plurality :of electric discharge paths and four three-'phaseStar-connected inductive networks displaced thirty electrical degrees,an interphaseftransformer comprising four legS each comprising ``twolmain lwinding Sections Vand zeach comprising `=two ``auxiliary windingSections, each of l:the main winding Sections being connected inSeriesfopposition with another main winding Section :on :a .differentleg land each 'of the auxiliary winding Sectionsbeing connected inseries oppo- Sition with an vauxiliary winding section on a difierentleg, land four lauxiliar `electric disch'arge paths connected Itotheauxiliary winding Sections.

8.511 combination, an alternating current circuit, azdirect Vcurrentcircuit having positive and negativaterminals, electric 'translatingapparatus connected hetween'said circuits and compris'ing a plurality ofelectric 'discharge paths and -n multiphase Star-'connected 'inductivenetworks -el'ectricallyaiisplaced 'fromzeac'h other, =an interphasetransformer comprising n legS each comprising two mainiwinding Sectionsand each comprising two auxiliary'winding Sections, each of the mainwinding Sections Vbeing connected in Series relation `with lanother mainwinding .section 'and a different 'leg and -each of the auxiliarywinding Sections being connected in Series relation lwith an zauxiliaryWinding *section =on a different leg, and n'.,auxi1iary'electricdischarge paths connected *'.to the auxiliary 'winding Sections.

-9. In combination, 'an 'alternating current circuit, :a fdirect'current circuit 'having positive and negative terniinals, elelectrictranslating apparatus :connected Abetween Said 'circuits fand comprisingVa gplu-ra'lity lof eie'ctric discharge pat'hs and n ,multi-phase'star-connected 'inductive networks-electrically displaced from eachother, an interphase ztransformer lcomprising n -legs each comprisingtwo fmain winding 'Sections and each comprising -two auxiliary windingSections, each of the ,main winding Sections 'being vconnected in.Series lrelation with another main winding Section and `a different leg'and 'each Vof fthe auxiliary iwinding Sections :being-connectedin'series relation .with ran ;au-xiliary winding 'Section -on fadi'-"erent leg, ithe ratio ;between the :turns of 'the auxiliary windingSections 'to Lthe fturns -of :the main 'winding :Sections :being 'as:follows:

'1 1 y 'rusin Sir-mir T -"1+1 Sin 1 where x represents 'theauxiliarywinding turns, y represents the main windingzturns, 417 Frepre-Sents -the number --of :phase windings in each network, andn'auxiliaif-y electric discharge :paths connected VVto 'the auxiliarywinding Sections.

10. JIn-combination, v'an alternatin'g current `circuit, a :direct:current 'circuit having :positiv'e and Vnegative terminalS, electrictranslating apparatus connected ,between Said :circuits :and compriSinga plurality'of electric `'discha'rge paths and n lmulti-'phasestar-connected "inductive networkselectricallydisplaced'from .eachother, each of Said networks comp-risin'gp zigzag-,phasewindings, ,'-aninterphase ltransformer zcomprising four legs each having two `main3winding lSections Iand each 'comprising `-two .auxiliary windingSections, each of Said rmain "-winding :Sections fbeing 'connectediniseries relation .withanother main winding section -on a different:leg -and 'each .auxiliary winding 'Section being connected in 'Series:relation with "an 'auxiliary windingsection Aon 'a :different leg, ;theturn 'ratio of :the zauxiliary winding Sections and the main windingSections'being approximately 2.-7,6,=.and n -auxiliaryelectric:discharge ,paths -connected to 2the vauxiliartz iwindinjg Sections.

v11. .In combination, Tan ralternating lfcnrrent circuit, a directA:current circuit having ;positive and negative terminals, electric`translating 'apparatusconnectedbetweensaid circuitsand'comprising a-plui'ality .of =electric discharge ;paths and a ,plurality -of'multi-;phase inductive :networks, ,interphase transforming meansbetween predetermined rgroups .of :said networks, an ;interphase.transformer connected between Said interphase transforming `means vandone terminal of .Saiddirect :current-circuit, an auxiliarynterphase.transformer 'comprisin-g a :magnetic :core Structure .having a'plurality of -legs corresponding .in .number ,to .the number -of l-Saidinductive networkaeach of Saidiegs lcomprising a pluralit-y of winding.Sections corresponding -in number =.to the number of v-Said networksand vbeing'connected to balance .Said au-xili-ary finterphasetransformer to prevent Satur'ation'of the core ;Structure, and aplurality of auxiliary electric discharge pathsconnected'to Saidfiwinding Sections.

VJOHN' W. BOAG. JOHN ``CJ. READ.

